Thermally conductive insulators

A thermally conductive insulator is a thin film that simultaneously transfers heat and blocks electrical current. It sits between a powered semiconductor (TO-220 transistor, IGBT module, MOSFET die) and a grounded heatsink, letting waste heat flow into the heatsink while preventing the package's internal voltage from shorting to chassis. The two specs that matter together are thermal conductivity (W/m·K) and dielectric breakdown strength (kV/mm) — neither value is meaningful in isolation for this product class.

Use a TIS dielectric film whenever the heat source has live voltage on its mounting tab or substrate. Discrete TO-220/247 packages, IGBT modules in inverters, RF power amplifiers on grounded chassis — all need isolation in addition to thermal transfer. A regular silicone TIF gap pad is electrically conductive at high voltages and would short the package to the heatsink. Conversely, if the heat source is already isolated (e.g. a CPU with internal die-to-package isolation), a TIF pad gives more conductivity per dollar.

The rule of thumb is 2× the working voltage with a 25 % safety margin, then verify against IEC 60664-1 / 61800-5 creepage and clearance tables for your insulation class. A 600 V IGBT module typically wants ≥ 4 kV breakdown across the insulator thickness; a 1200 V SiC module wants ≥ 6 kV. The TIS800 family covers up to 6 kV at 0.30 mm thickness. Don't rely on a single test pulse — partial discharge and long-term aging matter for production qualification.

TIS100 is a general-purpose silicone-rubber-on-fiberglass insulator for commercial discrete-device cooling — TO-220, TO-247, TO-263 — at 100–600 V working voltage. TIS800 targets industrial high-voltage modules: IGBTs, SiC, EV traction inverters at 600–1200 V working with 4–6 kV breakdown. TIS300 is a specialty conductive grade (graphite/Ni-plated) for combined EMI shielding and thermal transfer, and is NOT a dielectric isolator despite living in this category.

Yes. Most TIS sheets are kiss-cut on liner with optional pressure-sensitive adhesive (PSA) backing for SMT-style placement on the heatsink before module attach. Tolerance is typically ±0.1 mm on outline and ±0.05 mm on hole positions for production tooling. Send a DXF or STEP; tooling lead times are quoted per project. PSA-coated parts have a defined shelf life — confirm with the datasheet.

Classical mica washers offer good dielectric strength and price but require a separate layer of thermal grease and have brittle handling — they crack on overtorque. Modern TIS silicone-rubber-on-fiberglass insulators integrate the dielectric layer with built-in surface conformability, eliminating grease, simplifying assembly, and giving more repeatable thermal resistance after thermal cycling. Most new designs replace mica with TIS-class films.